Electric fuse



lMay 8, 1928o 1,669,157

G. R. BROWN ELECTRIC FUSE Filed July 30. 1926 invent or: George R. Brown,

His ttowmey.

Patented May 8, 1928.

UNITED STATES PATENT OFFICE.

' GEORGE R. BROWN, 0F BRIDGEPORT, CONNECTICUT, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPOEATION F NEW YORK.

ELECTRIC FUSE.

Application led J'uly 30,1926. Serial No. 126,052.

The present invention relates-to electrical safety devices and more especially to enclosed fuses.

The object of the invention is the provision of' 'an improved enclosed fuse subject to accurate rating and by whichthe electric circuit protected thereby shall be positively interrupted upon the occurrence of excess current conditions and without danger of injury to persons or things in the vicinity thereof upon such operation taking place.

It is customary to fill the space within 'an enclosed fuse not-occupied by the fusible element and its terminals with insulating material in granular or pellet form through which the heated gases evolved by the fusion or blowing of thefusible element are readis ly distributed and chilled and thereby tending-to the suppression of an electric arc and prevention of disruption of the fuse enclosure. It is also customary to employ more than one fusible element in a single enclosure where currents .of the circuits `to be protected are relatively large and are known as multiple link fuses. Such multiple link fuses heretofore in use have been found less reliable than singlelinlr fuses in that they fail to operate at their intended or rated capacities.

I have found that the main causeof uncertainty of operation at the rated capacities of multiple link fuses is that the spacing of the links, especially their central or reduced sections, varies between themselves and between them and the wall of the enclosure, and accordingly the dissipation of heat evolved by the links prior to fusion is variable. By my invention the spacing of the links is made certain irrespective of any inherent tendency to deflect or twist or because f unsymmetrical packing of the absorbent granular material about them in the enclosures.

One embodiment of my invention is shown in the accompanying drawing, -in which Fig. 1 is a, longitudinal section of the enclosure taken parallel to the plane of the fusible element; Fig. 2 is a similar section takenon a plane transverse to the plane of the fusible elements, and Fig. 3 is a central cross section. v

As shown, the enclosure consists of the usual tube 1 of insulating fibre with its ends closed by metal thimbles 2, through the ends of which terminal blades 3 freely pass. The

blades 3 have yoke pieces 4 rigidly attached thereto which are anchored at their ends to the inner wall of the tube by radial screws 5 which pass through the side walls of the thimbles 2 and the tube 1 and engage tapped holes in the yokes in the plane of the blades Set screws 6 disposed at right angles to the. plane of the blades 3 in threaded holes in the walls of the thimbles 2 and tube 1 serve to position and hold the blades in alignment.

Two fusible elements or links 7 are attached by rivets or solder or both tothe inner ends 8 of the terminal blades 3. The central portions of the links 7 are reduced in cross section by punching therein circular apertures 9 with narrow slits 1() extending therefrom longitudinally of the links for a purpose set forth below.

The means for spacing the central sections of reduced current-carrying capacity consists of a slab 11 of indurated fibre with parallel side edges and arcuate ends adapted to fit easily within the tube 1. Extending in from each side edge is a pair of spaced notches 12.

The spacer slab 11 is assembled in operative position by passing transversely endwise through the slits 10 in both fuse links 7 and upon spreading the latter to positions opposite the notches 12, the slab 11 is rotated on its axis through a right angle into the position indicated in each of the figures of the drawing so that the several reduced portions of the fuse links are closely surrounded by the walls of the respective notches 12.

The absorbent filling material 13, portion of which is indicated in Fig. 1, is inserted at one end of the tube 1, before the thimble 2 thereof is assembled and with the fuse in vertical position, it falls past the spacer at the sides thereof and distributes itself in the space below the spacer and thereafter the upper part is filled and thelinks completely surrounded and embedded therein in definitely spaced relation.

The fibre spacer serves also as an arc interrupter upon blowing of the fuse" in understood manner.

While I have shown and described herein the best embodiment of thc invention known to me, I do not desire to be restricted thereto.

What I claim as new and desire to secure by Letters Patent of the United. States, is

1. An electric fuse comprising an insulating tube, terminals vmounted on the ends thereof, fusible links having central apertures and connected Within said tube to said terminals, and a slab of insulating material of a length corresponding to the inner diameter of the tube and provided with spaced edge notches to receive therein the reduced portions of said links.

2. An electric fuse comprising an insulat- 10 ing enclosure having terminalsthereon, fusi- `ble links connecting said terminals through said enclosure and having central apertures with longitudinal slits extending therefrom, and a slab of insulating material extending through the apertures in said links and hav- 15 ing spaced edge notches for the reception therein of the reduced portions of said links. In Witness whereof, I have hereunto set my hand this 27th day of July, 1926.

GEORGE R. BROWN. 

